Many common antipsychotic medications and other prescription drugs inhibit the growth of “good” bacteria in the gut, possibly contributing to antibiotic resistant bacteria, according to the findings of new research.

In a study published last month in the medical journal Nature, German researchers found that about one-quarter of prescription drugs inhibited the growth of at least one strain of bacteria in the human microbiome.

Antibiotic medications have long been known to negatively affect the growth of the good bacteria in the human gut. However, the new study indicates non-antibiotic drugs can also negatively affect the microbiome, leading warn that this may result in increased proliferation of antibiotic resistant bacteria, or so-called “superbugs.”

Researchers from the European Molecular Biology Laboratory in Germany screened 1,000 marketed prescription drugs against 40 species of gut bacteria. Overall, 24% of the non-antibiotic drugs, or about 250 different drugs, inhibited the growth of at least one strain of bacteria in the human gut.

The study found that gut bacteria was especially sensitive to antipsychotic medications.

Different species of bacteria live in the human gut, or the microbiome. While every human has some common strains of bacteria in their gut, they also can carry different bacterial species. Researchers indicate different strains and species of gut bacteria may affect different functions in the gut. This may be similar to how different humans may have different responses to the same drug.

While it is unclear how the drugs target the microbiome, researchers emphasize the effects should be studied further in humans. The CDC recently funded antibiotic resistant bacteria research in order to boost knowledge of how the bacteria proliferates and whether anything can be done to mitigate the problem.

Researchers working on this recent study say this type of research could improve the knowledge of the effectiveness of existing drugs.

“The potential risk of non-antibiotics promoting antibiotic resistance warrants further exploration,” the researchers concluded. “Our results provide a resource for future research on drug–microbiome interactions, opening new paths for side effect control and drug repurposing, and broadening our view of antibiotic resistance.”